Strapping machine



Sept. 17, 1963 A. ERlcssoN ETAL 3,103,955

STRAPPING MACHINE Filed Aug. y?, 19Go 5 sheets-sheet 14 Sept-17, 1963 A.1.ER1cssoN ETAL 3,103,955

STRAPPING MACHINE Filed Aug. 17, 1960 5 Sheets-Sheet 2 g5 e? 7o 71 @e 7665' 1 5 INVENTORS A. l. ERlcssoN ETAL 3,103,955

Sept. 17, 1963 STRAPPING MACHINE 5 Sheets-Sheet 5 Filed Aug. 1'?. 1960 Sept. 17, 1963 A. l. ERlcssoN ETAL 3,103,955

STRAPPING MACHINE 5 Sheets-Sheet 4 Filed Aug. 1'7. 1960 l INVENTORS,

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Sept. 17, 1963 STRAPPING MACHINE 5 Sheets-Sheet 5 1211 @ggg-l5 Filed Aug. 17, 1960 la 113 135 92 9&1 93 1@ 95112 1 10c?" 10e 13 101 9 99 'f" r r' l lI 12o 129 127 12a/11e' 115/ 95 9@ United States Patent pany, a corporation of Delaware Filed Aug. 17, 1960, Ser. No. 50,242. 12 Claims. (Cl, Mtl-93.4)

The present invention relates to strapping machines and more particularly to portable tools for stretching, severing and sealing strap. The tools are adapted to enable the entire strapping oper-ation to be performed by an operator using a single tool.

Tools of the type under consideration are known 'and are illustrated and described in Patent No. 2,497,313 issued February 14, 1950 to John H. Leslie Il, and in Patent No. 2,594,397, issued April 29, 1952, to William C. Childress and Arvid L. Ericsson.

The present invention is directed to tools :of the type described in the above referred to patents and is more particularly directed to improvements -enabling tools of this character to be power-operated.

In known tools of the type under consideration fOr stretching, severing and sealing strap, the `strap is manually threaded into .the tool and is stretched to tension the strap around the object to be straped. A hand lever is then operated through -a forward and back stroke for the purpose orf: (1) feeding a seal lof the sealing jaws and positioning the sealing jaws about the overlapped straps; (2) cutting the top strap to complete the strapping operation; (3) crimping the seal to secure one another; and (4) returning all of the operating parts to their original position for the next strapping operation. As will be evident, a single lever is intended, upon operation thereof, to accomplish a plurality of complex functions and the present invention is particularly directed to providing power operation to replace manual operation of the prior art lever and thereby simplify tool operation and eliminate a manual manipulation requiring the application of considerable force.

It will be understood that the lever of the prior art which accomplished so many different `functions upon a single manipulation was required to move through a complex path and act in a complex manner in order to produce the desired eiiect and to return through a similarly complex path to its original position for the next strapping operation. Replacement of the prior art operating lever with power-operated means is, therefore, no simple task.

In accordance with the invention, a motor adapted t0 move a pinion through `approximately a 180 rotation 'and then return the pinion to its original position is coupled to the sealer pinion and mounted for movement in a vertical direction with the sealer pinion. The motor is preferably supported by the jaw support assembly which is vertically movable with the sealer pinion. The sealer pinion carries a cam positioned for Iengagement with a cam follower ixed to the tool body. The cam is shaped so that, upon rotation of the sealer pinion, the sealer pinion is first lowered to position a seal supplied from a magazine upon the `over-lapped straps, whereafter the sealer pinion is permitted to rotate without vertical movement to operate the crimping jaws. A cutter, mounted on the jaw support lassembly, cuts the upper strap adjacent the sealing area of the strap before the seal is positioned on the straps. The motor then reverses direction to rotate the sealer pinion in the opposite direction and the cam is shaped to automatically return the jaw support assembly to its initial elevated position.

In 'accordance with preferred practice of the invention, the moto-r is an air motor which functions to eiect rotational oscillation of the sealer pinion, eig., it rotates the the `overlapping straps to Patented Sept. 17, 1963 sealer pinion rst in one direction and then Iback to its initial position in the opposite direction. The air motor is desirably of the windshield wiper type in which a blade is air-operated to pivot iirst in on direction and then back in the opposite direction. This windshield wiper type air motor is preferably supported lby the jaw support assembly with the pivot of the blade being connected to the sealer pinion whereby pivotal movement of the blade causes rotation of the sealer pinion. tInstead of a windf shield wiper type air motor, lan air motor having la piston which reciprocates longitudinally across an air cylinder and which is provided with la rack engaging the sealer pinion to rotate said pinion in one ydirection on the forward stroke of the piston, and then to return said pinion to its initial position by rotating the same in the opposite direction upon lthe rearward movement of said piston may also be used. While air-powering means yare preferred, other powering means such as an electric motor may be used and suitable switches provided to reverse the direction of rotation of the electric motor when opposite rotartion of the sealer pinion is desired. Irrespective of the motor selected, the motor is mounted for vertical movement with the sealer pinion and the motor operates to rotate the sealer pinion rst in one direction and through Y an are of about and thereafter in an opposite direction to return the sealer pinion through an Aoppositely directed arc to its initial position. Thus, the air motor `is free to move vertically with the jaw support assembly which moves up and down with the movement of the sealer pinion as dictated by the action of the cam which is carried thereby. l

The cam which controls the movement of the sealer pinion is formed with a recess bounded by an overhanging portion which bears downwardly upon the iixed cam follower to elevate the sealer pinion and the jaw support assembly therewith and by a lip which bears upwardly against the cam follower. The cutter, carried by the jaw support assembly, severs the upper strap adjacent the sealing area as the jaw support assembly is moving downwardly, before the seal is applied to the strap. Beneath the recess and adjacent the lip, the cam is (formed to deine a circular path so that, when the cam follower is on the back side of the cam with the jaw support assembly in lowered position, the sealer pinion may be rotated to operate the sealing jaws without vertical movement `of the jaw support assembly. The circular portion of the cam terminates at a point positioned approximately 180 removed from the recess. When the direction of rotation of the sealer pinion is reversed, the rotation of the cam is yalso reversed and the overhanging portion thereof moves into position above the :cam 'follower to raise the cam as the sealer pinion returns to its initial rotational position and thereby elevates the sealer pinion and the jaw support assembly to their initial most elevated position.

rllhe sealer pinion is formed with enlarged gear teeth over `a portion of the circumference thereof so that the sealer pinion will engage with the teeth of a rack which operates the crimping jaws only when the sealer pinion is moving over a limited portion of its rotational movement. -In this manner, the crimping jaws are closed after the downward movement of the jaw support lassembly which is effected during the iirst rotational movement Otf the sealer pinion and then the jaws are opened prior to the upward movement of the jawr support assembly which is eected during the second reversely directed rotational movement of the sealer pinion.

T he invention includes the specific structure of the windshield wiper air-motor which permits the sealer Ipin-V ion to be moved through a 180 arc `and then Iautomatically returned to its initial position. The initial movement of the sealer pinion is preferably effected in accordance with the invention by the mere depression of a trigger, it being unnecessary to maintain the trigger in its depressed position while the` air motor operates to cause the sealer pinion to be rotated in the manner indicated.

The inventionwill be more fully understood and its operation and advantages appreciated from the description which follows taken in conjunction with the accom panying drawings in which there is shown a portable tool forming an illustrative embodiment of the invention, in which each yand every detail shown is incorporated as a part of this speciiication, in which like reference numerals refer to like parts, and in which:

FIGURE 1 is a perspective view of a portable tool provided with air powering means and constituting one form of the invention;

FIG. 2 is a partial side elevation, in section, taken through `the jaw assembly support looking ttoward the rear of the tool and showing the sealer pinion and its relation to the air motor for operating the same, the sealing jaws, the pinion-operated cam and the mounting of the air motor for vertical reciprocaton with the sealing pinion;

FIG. 3 is lan elevation looking at the tool from the back thereof, pants being broken away and in section to show the construction of the windshield wiper type air motor;

FIG. 4 is a cross-section on the line 4-4 of FIG. 3;

FIG. 5 is a cross-section on the line 5-5 of FIG. 4 and showing the details yof the valve 'assembly for operating the windshield wiper type air motor;

FIG. 6 is a cross-section similar to FIG. 5 and showing the valve assembly after the trigger thereof has been depressed to operate the same;

FIG. 7 is a fragmentary side elevation taken on the line 7-7 of FIG. 4 yand showing the automatic valve stem release mechanism;

FIG. 8 is a section taken on the line 8-8 of FIG. 6;

FIG. 9 is a perspective view showing the base plate and the inner wall of the windshield wiper-type air motor, these parts being swung apart to show the manner in which they fit together;

FIG. 10 is a perspective view of the pivotal blade which operates within the windshield Wiper-type air motor;

FIG. 11 is a partial side elevation showing the sealing mechanism prior to operation thereof;

FIG. 12 is a partial side elevation similar to FIG. 11 and showing the sealing mechanism during operation and after the jaw support assembly has been lowered by the action ofthe sealer pinion-operated cam and showing the sealer pinion rotating without further vertical movement to enable the sealer pinion to engage the crimping jawoperating rack;

FIG. 13 is another partial side elevation similar to FIG. 1l and showing the sealing mechanism at the completion of the operating stroke with the jaw support aS- sembly;

FIG. 14 is a cross-section taken on the line 14-14 of FIG. 11 and illustrating structural details of the sealing assembly;

FIG. 15 is a fragmentary perspective exploded view, similar to FIG. 9, showing a motor wall and bottom for another valve assembly;

FIG. 16 is a cross-sectional view, similar to FIG. 5, showing another valve mechanism for use with the arrangement of FIG. 15, the valve stem being shown in itS outermost position;

FIG. 17 is a fragmentary detail perspective view, showing the valve stem latch and the valve stem in the position of FIG. 16;

FIG. 18 is a cross-sectional view, similar to FIG. 16, wih the valve stem depressed to its innermost position; an

FIG. 19 is a fragmentary front elevational View, showing the latch holding the valve stem in intermediate position.

Referring to the drawings and particllarly to FIG. l, the tool of the invention includes `a base or frame 10 which is intended to be rested upon a package to be strapped and which carries the operating mechanism. The operating mechanism includes, at one end of the base 10, a gripper assembly 11 operated by lever 12 for the purpose of anchoring the lower end of the package-encircling strap to the tool base. At the other end of the base 10 is a serrated or knurled stretching wheel I13 which is pivotally mounted at 14 for pivotal movement toward and away from a slide plate or wear pad 15, the stretching wheel 13 being intended to engage and bite into the upper end of the package-encircling strap and to stretch the strap tight when the wheel 413 is rotated as by actuation of air motor 16.

It should be understood that the particular mechanisms illustrated for anchoring the lower end of the strap and for stretching the upper end of the strap are known and are not essential to the present invention which simply requires that the strap encircling the package to be strapped be tensioned with the overlapped portions thereof positioned above an intermediate portion of the base plate below the sealer mechanism. In the preferred embodiment of the invention, the intermediate portion is dened by an opening or recess 17 in the base `10. Thus, the specific structure of the gripper assembly 11 is known and not material to the invention. Similarly, the specific structure of the stretcher `13 is known and not material to the invention although it -is preferred to employ a power-operated continuous stretcher of the type shown and which is adapted to employ strap from a coil thereof. Since the invention employs air power as the preferred power source for the sealing and cutting operations, it is preferred that the stretching wheel :13 be air-driven.

Referring further to FIG. 1, the operating mechanism includes crimping jaws 18, a magazine 19 for storing a stack of seals, a seal ejecting mechanism 20 for delivering the lowermost seal in the stack to the crimping jaws 18 for application thereby to the overlapped strap ends. A cutting mechanism 21, carried by the crimping jaws 18, severs the -upper strap adjacent the sealing area before the seal is applied to the strap. The base E10 of the hand tool includes an upstanding portion 22 upon which the various operating mechanisms are mounted. The hand `tool also includes a carrier handle r23) having a hook-receiving opening l24, `and means for power-operating the mechanism for cutting and sealing the overlapped strap ends including the windshield wiper-type air motor generally identified by numeral 25.

Referring to FIG. 2, the crimping jaws 18 are pivotally connected to a jaw support assembly generally identified by the numeral 26 and are carried thereby. The jaw support assembly is mounted for vertical movement with respect to the opstanding portion 22 of the tool base or frame 10.V A sealer pinion 27 is horizontally rotatably mounted in aligned apertured bearings 28 in the jaw support -assembly 26 and moves vertically with it. The sealer pinion l27 extends through a slot 29 in the upstanding portion `22 to permit vertical movement of the sealer pinion 27 with respect to the tool body.

The specic structure of the crimping jaws 18 forms no part of the present invention. It is important only that these jaws are adapted to receive a seal supplied thereto and that they are adapted for operation upon vertical movement of an operating mechanism including a rack as will be explained more fully hereinafter.

As will be seen in FIG. 2, a connecting member 33 is secured to the upper end of the jaw support assembly l26 and the air motor 25 is secured to the connecting member 33 by means of bolt 34. The connecting member 33 is L-shaped and extends through the opening defined by the carrier handle 23 to connect with the motor 25 at the back of the tool. It will also be seen that the sealer pinion 27 extends into the motor 25 for rotation thereby. The connecting member 33 and the sealer pinion 27 securely mount the motor 25 at the back of the tool for vertical reciprocation with the jaw support assembly 26.

The sealer pinion i27 carries a cam 30 which is secured to the outer extrem-ity of the sealer pinion 27 by the nut 31 and washer 312. The shape of the cam 36 can be seen in FIGS. `1 and 3. The cam 36 is formed with an outer periphery having an overhanging portion 35 and a lip 36 which define a recess 37 adapted to receive a follower 33 which is xed to the upstanding portion 22 of the tool body. The cam 30 further includes a circular portion 39 adjacent the lip 36 and terminating at a point itl spaced about 180 from the recess `37.

The cam 30 rotates with the sealer pinion 27 by operation of the motor 25 and the angular position of the cam 30 regulates the vertical level of the sealer pinion `27 and the ja-w support assembly A26.

It lwill be seen in FIGS. 1 and 3 that the air motors l@ and 25 are supplied with air from a common source through the air line 4t2 and thence, through the T connection 43 and tair lline 4dto the air motor 25. Air motors lr6 and 2S include operating triggers 45 and 46, respectively, for actuating the same.

The Windshield wiper-type air motor 215 is illustrated in FIGS. 3 and 4, where it 'will be seen that the air motor 25 comprises a semi-cylindrical chamber 47, a valve assembly 4S, including ian operating button 49 and a pivotaily mounted blade lil.

A portion of the air motor 2S is broken away in the back view of FIG. 3 in order to reveal the operating blade il which is secured to the sealer pinion 27 and which swings to rotate the sealer pinion about its longitudinal laxis through an arc of about 180, 'and then back again through the same arc to its initial position.

'Ihe chamber 47 has an inner wall 56 which includes the valve mechanism 46 and which is secured to a semicylindrical housing 5l by screws 52 and to a base 53 by means of screws 54. The housing 5l is secured to the base 53 by means of screws 55. The base 53` is strengthened by .a Web 56, which also serves as a linger guard to prevent pinching when operating the tool.

The details fof the valve mechanism litare shown in FIGS. 5, 6, 7, 8 and 9'.

Referring more particularly to FIGS. 5 and 6, it will be seen that the valve mechanism 4S includes a valve housing 5,7 having an air supply bore 5S, which communicates with air supply line 44, shown in phantom, and a valve stemreceiving bore 5 9 within which the valve stem 6d is slidably mounted for longitudinal movement. A spring 6l seaited at the bottom of the bore 59 biases the valve stern '6d outwardly into trigger-opening position as illustrated in FIG. 5. The air supply bore 53 communicates by means of bores 62 and 63 with the stemarece-iving bore 59. The stem 60 is formed with a pair of spaced apart circumferential recesses or reduced portions 61M and 6%, the innermost 66a of which communicates with the air supply bores 62 or 63, selectively, and the outermost 6b tof which communicates with the exhaust bores 64 and 65, selectively, to form air supply and exhaust valve passages, respectively.

To facilitate description, it will be understood that the blade 4l divide-s the semi-cylindrical space dened by the motor chamber 47 into two sides, a lirst side adjacent the valve mechanism 4S rand a second side remote from the valve mechanism `4.8. These respective sides are indicated by the numerals #l and #2 in FIG. 3.

Prior to operation of the motor 25, the blade 41 is at its stop position adjacent the valve mechanism 41S, as illustrated in FIG. 3, the valve stem 66 is positioned :as shown in FIG. 5 and the trigger 46 is in its open position. When the trigger 46 is pivotally depressed, the button 29 is pushed inwardly of the valve mechanism d5 and the stem 60 is moved to its innermost position, as shown in FIG. 6, compressing the spring 61. The inner circumferential recess a of stern 60 then interconnects bore 62 with port 66 to enable air supplied through the air line 44 to pass successively through the .bore 58, the bore 62, the inner ycircumferential recess 60a and the port 66 through which it enters the portion of the air chamber of the motor 25 designated .ii-1 behind the blade 41. This causes the blade 4l to swing or pivot toward side #2 about the axis of pinion 27 and to rotate the pinion. The blade 411 is secured to the pinion by means iof a splined connection 41a.

When air is supplied to side #1 of the motor 25 to pivot the blade Ail, air must be exhausted from side #2 as the blade `lil swings through its arc of approximately 180. For this purpose the base 53 is formed with a longitudinal channel 167 which communicates with side #2 through a bore 68 in inner Wall 56 (see FIG. 9). The exhaust gases forced out of side #2 pass through the bore 68 and into the exhaust bore via the longitudinal channel 67 and an offset recess 65'. The exhaust bore 65 communicates with one of the two exhaust ports 69 via the outermost circumferential channel 69h in the valve stem 60* as shown in FIG. 6.

A valve stem latch and release mechanism rwhich renders the pivotal oscillation of the blade 41 automatic is shown in phantom in FIGS. 5 and 6. The latch and release mechanism holds the valve stem in a depressed position until the yblade il has moved fully through its arc ont labout 180 to side #2 and thus is eilective to insure operation of the tool through its complete cycle each time that the valve button 49 is depressed suiciently to cause the latch and release lmechanism to grasp the valve stem. This insures that the operator fof the tool will not so operate the tool that a seal will be improperly or incompletely crimped. It further relieves the operator of the obligation of holding the trigger depressed until the complete initial swing .of the blade 4l has been accomplished. Thus, the operator need only squeeze the trigger 416 fully and then release the same whereupon the motor 2S will operate through its full forward and back swinging sequence.

The latch and release mechanism includes an arm 70 having a latch 73 on one end thereof. The arm 79 is pivotally mounted on a pin 7l. and is spring biased by a spring 72, seated in a recess 72a: in valve housing 57 into the valve stem engaging position shown in FIG. 6. The latch 73 engages a shoulder portion of the valve stem 69 `adjacent the button i9 to hold the valve stem 60 in a depressed position until the motor has completed the rst half tof its cycle fof movement.

To more `fully illustrate the catch and release mechanism, this mechanism is shown in elevation in FIG. 7 and the relative positioning of the recess 72a and the valve stem receiving bore S9 is shown in FG. 8. As shown in FIG. 7, vthe catch 73 extends inwardly of valve housing 57 and is vertically movable with the arm 7i? through slot 73a.

As the blade il swings lfrom the position shown in FIG. 3 to its position of maximum movement remote from the valve mechanism 418, the sealer pinion 27 is rotated as indicated by the arrow 74 (see FIG. 6). When the blade el reaches the end of its stroke, a projection 27a (see FIG. 7) on the sealer pinion enga-ges and elevates the inner end of the `arm '70l to pivot the arm 7d` aga-inst the biasing force of spring 72. This moves the catch 73 downwardly out of engagement with the Valve stem 69 and permits the spring 6l to slide the freed valve stem 69 outwardly along the valve stem-receiving bore S9 into the position shown in FIG. 5.

Movement of the valve stem 6d from its position shown in FIG. 6 to its initial position `shown in FIG. 5, closes the bores 62 yand 65 and opens the air supply bore 63 yand. the exhaust bore 676i. Air is then supplied through the air supply bore 63 around the inntermost circumerential recess 63:1 i-n the valve stem 60 to the air supply bore 75 from which it passes via the offset recess 76 to the ohannel 67 and thence through bore 68 to side #2 of the air motor 25. Thus, when the blade 41 ends its initial swing to a position remote from the valve mechanism 48, the valve stem 60 is automatically repositioned and air is supplied to side #2 for the return swing of the blade 41 to its initial position shown in FIG. 3. Exhaust from side #l is elected directly through port 77 and bore 64 to the second exhaust 69 `which communicates with the outermost circumferential recess 60h in the valve stem 60 when this valve stem is positioned as shown in FIG. 5.

Referring to FIG. 9, the interconnection between the inner wall 50 with its valve mechanism 48 and the base 53 containing the longitudinal channel 67 is illustrated by opening these parts fand swinging them through an arc, the swing of the parts as well as the registered position of some of the bores such as the bores 65, 75, and 68, are indicated in FIG. 9 by means of the arrows 7 S.

The swinging blade 41 is pictured in FIG. l0 where it will be seen that the blade 41 includes an enlarged inner end 79 which is bored and splined at 41a to receive the toothed or splined extension of the sealer pinion 27. The blade portion 80 is Iformed with stops 81 on each side thereof (see also FIG. 3). A peripheral channel in the edge of the blade portion 80 carries a rubber gasket 82 which provides a seal with the interior surfaces of the chamber 47 of the air motor 25.

The extension of the sealer pinion 27 which passes through the bl-ade 41 also passes through Ia `bearing 83a (see FIGS. and 6) in an opening 83 in the inner wall 50 so that the blade 41 is mounted for swinging movement about the center of the base 53. To prevent communication of air between side #l and side #2 behind the enlarged portion 79 of the blade 41, the inner surface of base 53 is channeled as indicated at 84 and a gasket is inserted in the channel 84 to bear against and form a seal with the enlarged portion 79 `of the `blade 41. The opening 83 is suitably packed `as with end rings to prevent leakage of -air therethrough.

To brieliy summarize valve operation in accordance with the invention, the valve mechanism 48 is initially in the position shown in FIG. 5. Depression of trigger 46 thrusts valve stem 60 inwardly until spring 72 pivots arm 70 to cause the catch 73 to hold the valve stem 60 in the position shown in FIG. 6. When this happens, air passes from the supply 44 to the port 66 and into side #l to swing the blade 41, air exhausing from side #2 via lbore 68 and longitudinal channel 67 and exhaust bore 65 to the exhaust 69. When the initial swing of blade 41 is completed, the arm' 70 .is automatically pivoted to release catch 73, and spring 61 returns the valve stem 60 to its initial position shown in FIG. 5. Air is then supplied through bore 63 to channel 67 via offset 76 and thence through bore 68 to side #2 to swing blade 41 back to its initial position. Air exhausts from side #l on the return stroke of blade 41, through port 77 and thence to the exhaust 69.

In the manner described above, the sealer pinion 27 is caused to rotate approximately 180 in a first direction and then t0 return through an opposite `swing to its initial position. In view of the mounting of the air motor for vertical movement with the sealer pinion 27 as is lbest shown in FIG. 2, the rotational oscillation of sealer pinion 27 is permitted despite the fact that the elevation or vertical movement of sealer pinion 27 is independently controlled.

The sealing action which is achieved by operation of the windshield wiper-type air motor 2S upon the overlapped strap ends for the purpose of severing the upper strap adjacent the sealing area, applying a seal, and then crimping the seal to complete the sealing and crimping operation is illustrated in FIGS. 1114.

Referring rst to FIG. 1l, the operating blade41 of the air motor 25 is shown in its initial position prior to operation of the air motor. rI'he cam 3i) which is carried by the sealer pinion 27 is in a position in which the follower 38 is within the recess 37 so that the overhanging portion 35 of the cam 30 is above the follower 38 to maintain the sealer pinion in elevated position. The jaw support assembly 26, the crimping jaws 18, and the air motor 2S are all in elevated position as determined by the position of the sealer pinion 27.`

The jaw support assembly 26, as shown in both FIGS. 11 and 14, comprises a body portion 85 which is formed with a vertically extending cylind-rical 4bore 86 within which a crimping jaw actuating rack 87 of semi-circular cross-section is slidingly mounted for vertical movement. The bore 86 partially intersects with the path of the sealer pinion 27 extending through the bearings 28. The sealer pinion 27 is formed with short teeth 88 and also with long teeth 89, the long teeth 89 extending over a segment of the circumference of the pinion 27 and being of suioient length to engage with the teeth 90 of the rack 87. The short teeth 88 are not of sufiicient radial length to engage rack teeth 98. In this initial position illustrated in FIG. 11, in which the :operating blade 41 has not yet been moved, the long teeth 89 are not yet in a position to engage the teeth 90 on the rack 87.

When the air motor 25 is actuated, the operating blade 41 lirst swings in a counter-clockwise direction in FIG. ll. The swinging movement of blade 41 lis transmitted to the sealer pinion 27 causing the cam 30 to rotate in a counter-clockwise direction thus removing the overhanging portion 35 from above the follower 38 and causing the lip 36 of the cam 30 to bear against the follower 38 to thrust the sealer pinion 27 downwardly. As the sealer pinion 27 rotates in a counter-clockwise direction, it will move downwardly and carry with it the jaw support assembly 26, the crimping jaws 18, and the cutting mechanism 21. Since the connecting member 33 is bolted to the body of the jaw support assembly 26, as indicated at 91, the air motor 2S will also be lowered. After the sealer pinion 27 has been lowered suiciently to permit the lip 36 of cam 30 to rotate past the follower 38, further rotation of the sealer pinion 27 by the operating blade 41 does not result in any further change in the elevation of the sealer pinion 27 or of the cutter mechanism, since the follower 38 bears against the circular portion 39 of the cam 30.

At this point, and as illustrated in FIG. 12, the cutter 21 has cut the upper strap and the crimping jaws 18 with a seal therein, have been lowered about the overlapping strap ends, the seal having been supplied to the crimping jaws 18 from the magazine 19 as elsewhere herein described.

As can be seen in FIG. 12, the initial counterclockwise swing of the blade 41 has not yet been completed and the long teeth 89 on the sealer pinion 27 have just begun to engage the teeth on the rack 87 for ythe purpose of thrusting the rack 87 downwardly to cause the crimping jaws to close and crimp the seal about the overlapped strap ends. As illustrated in FIGS. 2 and ll-l4, the lower end of the rack 87 is pivotally connected with the pin 18a so that, when rack 87 is moved downwardly, the links 18b are opened and the crimping jaws are pivoted about pivots 18e to close the same. When the rack 87 is later elevated, the opposite action takes place and the crimping jaws are opened to release the sealed strap.

FIG. 13 illustrates the completion of the counterclockwise swinging movement of the blade 41 in the air motor 25 in which position the teeth 90 have thrust the rack 87 to its lowermost position driving the jaws 18 downwardly to complete the crimping operation.

T-he direction of rotation of the operating `blade 41 is then reversed and the blade 41 rotates in a clockwise direction causing a clockwise rotation of the sealer pinion 27. The long teeth 89 engage the teeth 90 on the rack 87 to elevate the rack and thereby open the crimping jaws 18 to release the seal. Further rotation of the sealer pinion 27 in a clockwise direction causes the overhanging portion 35 of cam 30 to engage the upper end of the -follower 38 to elevate the sealer pinion 27, jaw support assembly 26, cutting mechanism 21 iand the air motor 25, ,and thereby return the structure to its initial position `as shown in PEG. 11. rThe tool can then be removed from the completed strapped package and, upon removal, is ready to eiect the next strapping operation.

Referring more particularly to FIG. 14, it will be seen that the body 8S of the jaw support asse-mbly 26 is slidlably mounted for vertical movement with respect to the opstanding portion 22 of the frame 1Q, these two parts being interlocked in `a tongue and groove manner a-s pictured. The left hand portion of the body 35 is similarly interiitted with the magazine 19.

In overall operation, the operator straps an object to be strapped securing the lower strap end using the gripper assembly 11 and holding the upper strap end beneath stretching Wheel 13, the air motor 16 being pivotetd about pivot 14 to cause the wheel 13 to engage the upper strap end against wear pad 1S. The operator then presses trigger 4S to rotate stretching wheel 13 toA tension the strap about the object to be strapped and provide overlapped strap ends above the opening 17.

When the above has been completed, the operator merely depresses trigger 46 to operate the windshield Wiper type vair moto-r 25 causing the 'blade 41 to swing counter-clockwise as viewed from cam 3@ through an arc of about 180. This causes the entire jaw mechanism to move downwardly to position the -seal about the ove-rlapped strap ends. As the jaws are moving downwardly to position the seal, the cutter 21 `severs the upper strap adjacent the area where the seal is thereafter applied. The rack S7 is then thrust downwardly to crimp the seal. At the end of the counter-clockwise swing of blade 41, the release arm 7) is moved by sealer pinion 27 to release catch 73 -so that valve stem 60 is moved to open trigger do and blade 41 is swung clockwise to its initial position, the rack 37 being iirst elevated to open jaws 18 and the sealer pinion and associated parts being then elevated by overhanging portion 35 of cam 31B. As the jaws are being moved upwardly, the seal `ejecting mechanism moves a seal from the magazine 19 into position between the jaws 13 for the next sealing operation.

The embodiment of FGS. 15-19 is identical to that of FGS. 1-14 except for the valve mechanism and the valve stem latch and release mechanism. The rest 'of the strapping machine structure is common to .bo-th embodiments of the invention.

1n the embodiment of FIGS. 15-19, the valve mechanism includes a valve housing 92 having lan air supply bore 13 which communicates with an air lsupply line 94 and a valve stem receiving bore 95. The bore 9S is counterbored just inwardly of the air supply bore, and an iannular valve sea-t 96 is mounted adjacent the annular shoulder 97 formed by said counterbore. A cup-shaped plug 98, mounted in the counterbore, has an outer end 99 forming a closure for the bore 9S. The end 99 is provided with an aperture 1h11.

A valve lstem 191, slidably mounted in the bore 95, has an operating button 102 extending outwardly from its outer end and projecting through the aperture 1111i. A trigger 103 is pivoted to the housing 92, as indicated at 104i-, for operating engagement with the outer end of the button 102. A collar 1115 is fixed to the button 102 within the cup-shaped plug 98. A coiled spring 1116 encircling the operating button 1112 between the rear side of the valve seat and the inner surface of the collar 165 urges the valve stem outwardly, into the position shown in FIG. 16. Another spring 1116 seated in the inner end of bore 95 also urges the valve stem 101 outwardly toward a closed position. In this position, the valve stem is in engagement with the valve seat 97, and the valve is at rest.

The valve stern 101 is provided with three longitudinally spaced circumferential recesses 107, 10d and 199.

1G When the trigger 193 is depressed, the valve stom is moved inwardly, and air from the air supply bore 93 flows into the bore 95 rearwardly of the valve stern. Three bores 119, 111 and 112, communicating with the valve stem receiving bore in longitudinally spaced areas, are interconnected at one end to a common bore 113. The inward longitudinal movement of the valve stem causes air from the air supply bore 93 to flow through the portion of the bore 95 rearwardly of the valve stem 101 and into the bore 113 through the bore 111i.

As shown in FiG. 18, the bores 11d, 111 and 112 eX- tend through the bore 95 and are continued on lche other side, as indicated at 114, 11S and 116, respectively. The bore 114, is closed at its lower end and does not provide any exit for the air. When the trigger 103' is depressed, it moves the valve stem into the position shown in FG. 18, in which the bore 115 is cut oit from the bore 111 by the valve stem, and the bore 116 interconnects the bore 112 with the port 117 to direct the iiow of air into side #l of the motor 25. This causes the blade 41 to swing on pivot toward side #2 about the axis of pinion 27 and to rotate the pinion in the same manner as in the embodiment of FIGS. 1-14.

As the blade 41 swings toward side #2, the air is eX- hausted from side #2. The valve housing has a base 1115 having a channel 119 provided with three longitudinally spaced notches 121i, 121 and 122. The notches 1211, 121 and 122 interconnect the channel 119 with the bores 123, 125 and 115, respectively, in the inner wall 12d.

When the valve stem is in the position shown in FIG. 18, in which air under pressure is flowing from bore 93 through various bores including bore 116 and through the port 117 into side #l of the motor, the upper end of the bore 115 is olosed ot by the valve stem. The air from the channel 119 must therefore exhaust through the bore 125. The bore 125 terminates in the bore 9S, but in the position of FlG. 1() it communicates through the circumferential recess 1119 with the return chambers exhaust port 126.

yWhen the blade 41 reaches the end of its stroke, the cam latch and release mechanism hereinafter described, moves the valve stern 101 to an intermediate position in which the valve stern is spaced slightly from the valve seat 96 to allow air to low from bore 93 through the gap between the valve seat and the outer end of the valve stem. The intermediate position is very close to the fully closed position, and lthe various bores in the valve housing and circumferential recesses in the valve stern are positioned as indicated in the fully closed position of the valve shown in FIG. 16.

lln the intermediate position of the valve stem, the air under pressure iiows into the bore 113 just as when the valve stem is in the fully open position of FIG. A18. The bore 116 is shut off from the bore 112 by the valve stem, and the lair hows from bore 113 through the bore 111, circumferential recess 107 and the bore 115. From the bore 11S the air flows through channel 119.

The bore 125 is closed by the valve stem 101 and, therefore, the air ilovvs from the channel 119 through the notch and into the bore 123. The bore 123 directs the flow of air into the side #2 of the motor 25, thereby causing the blade 111 to swing or pivot toward side #l about the airis of the pinion 27. As the blade 41 swings toward the side #1, the air is exhausted from side #l through a bore 127 and a main chamber exhaust port 12S.

The valve housing 92 is provided with an elongated recess 129 adjacent the inner end of the valve stem 10'1. The inner end portion of the valve stem Vis provided with a threaded yrecess (not shown), and a block 131) is secured to the valve stern by a screw 131. The block 13@ has a lug 132 that projects into the recess 129 and is slidable therein.

A latch 133, pivoted to the valve housing as indicated at 134, is located to pivotally move between the block 1313 and the adjacent surface of the valve stem 101 to en- 1 l gage the lug 132. A spring 135 seated on a tit 136 projecting upwardly from the upper edge of the latch has its other end bearing against a fixed cup 136 to urge the latch pivotally downwardly into engagement with the lug 132.

The lower edge of the latch is notched, as indicated at 137, 138, and 140, to provide a series of surfaces at different levels. A projection 141 is formed on the end of the latch remote from its pivot, and another projection 142 is provided between the notches 133 and 139. A cam 143 pivotally mounted on the pinion shaft for the motor vane as indicated at 144, has a cam surface 145 adapted to engage the surface of Ithe projection 142 when the cam and pinion shaft are rotated counter-clockwise and adapted to engage the surface of the notch 137 when the cam is rotated clockwise.

In the closed or rest position of the machine, the projection 141 rests on the upper edge of the lug 132 and the springs 106 and 106' urge the valve stern into the closed position shown in FIG. 16. When the trigger 103 is pressed inwardly, the valve stem is moved inwardly far enough yto align the lug 132 with the notch 139. The spring 135 moves the latch pivotally downwardly until the notch 139 engages lthe lug 132 and holds the valve stem in the position sohwn in FIG. 18.

When the valve stem is in the position of FIG. 18, it directs the flow of air, as hereinabove described, to cause motor 25 to rotate the blade 41 in la counter-clockwise direction. The cam 143 moves pivotaily with the blade 41, and engages the projection 142 when the blade 41 reaches the limit of its counter-clockwise rotation. The engagement of the cam surface 145 with the projection 142 moves the latch 133 pivotally upwardly far enough to disengage the notch 139 from the lug 132, but not far enough for the lug 132 to clear the projection 141. Accordingly, the springs 106 and 106 move the valve stem outwardly toward its closed position and the lug 132 moves into engagement with the side of projection 141 `which is urged downwardly by the spring.

As shown in FIG. 19, the projection 141 is comparatively narrow, and the valve stern is held against movement to the fully closed position by the width of said projection. When the latch stem is held |in this position, the ow of air is, as previously described, directed to fthe motor in such a direction as to reverse the motor and rotate the blade 41 `and the cam 143 in clockwise direction. As the blade 41 approaches the end of its movement in clockwise direction, the cam surface 145 engages the notch 137 of the latch and lifts it to cause the projection 141 to clear the lug 132. The springs 106 and -106 then move the valve stem into completely closed position and the machine is in position for another operation.

Although we have described two illustrative embodiments of the invention in considerable detail, it will be understood that the description thereof is intended to be illustrative rather than restrictive, as many details of construction may be modified or changed without departing from the spirit or scope ofthe invention. Accordingly, we do not desire to be restricted to the exact constructions described.

We claim:

1. In ,a strapping machine comprising means to supply, position and crimp a seal about the overlapped ends of a str-ap, the improvement which comprises a jaw support assembly mounted for ver-tical reciprocation, crimping jaws connected to said jaw `support assembly, a sealer pinion rotatably mounted in said jaw support assembly for vertical movement therewith, said jaw support assembly including means operated by rotation of said sealer pinion for opening and closing said crimping jaws, cam means carried by said sealer pinion and engageable with a cam follower secured to said machine for vestically moving said sealer pinion and said jaw support assembly in response to the rotational position of said sealer pinion,

an air-operated motor of a windshield wiper type coupled to said sealer pinion and -mounted for vertical movement with said sealer pinion, said motor comprising a blade connected to said sealer pinion and mounted `for back and forth movement to rotationally oscillate said sealer pinion and valve means yfor regulating the supply of air to said motor to cause said blade to swing in one direction, said motor including means operative upon swinging movement of said blade through an arc of about from its initial position in said one direction to reverse the position of said valve 4to thereby cause said blade vto swing back to its initial position and to remain there, and a connecting member secured to said jaw support assembly and extending to the side thereof remote from said cam means and said motor being secured to said connecting means on lthe side of said jaw support assembly remote from said cam means.

2. An improvement as recited in claim 8 in which said ywindshield wiper type air motor comprises a semi-cylindrical chamber surrounding said blade and a valve housing formed with an `air supply bore, `a valve stem-receiving bore, a pair of bores communicating between said air supply bore and said stem-receiving bore, a pair of bores opposite said first named pair of bores and a pair of exhaust bores communicating with said stem-receiving bore, :an operating trigger extending over said valve stemreceiving bore, a valve stem slidably fitted in said valve stem-receiving bore and formed with a pair of [longitudinally spaced means permitting the passage of air across `said stem spring means biasing said valve stem into va trigger-opening position closing one of said bores communicating between said air supply bore and said valve stem-receiving bore and permitting passage of air through the outer of said bores to said chamber on `a first side of said blade and opening the exhaust bore connected with said chamber on the second side of said blade to atmosphere, latch -means for holding said valve stern against the pressure of said spring upon depression of said trigger, said valve stern being positioned by depression of said trigger to close -the other of said bores communicating between said air supply bore and said valve stem-receivin g bore and permit passage of air through the first of said bores to said chamber on said second side of said blade and opening the exhaust bore connected with said chamber on the rst side of said blade to atmosphere, and means to release said latch to free said valve stem after said 'blade has swung from one side of said housing to the other side thereof.

3. An improvement las recited in claim 2 in which said latch is `spring biased against said valve stern and means movable with said blade and sealer pinion are provided yfor automatically releasing said latch when said blade completes its initial swing.

4. An improvement as recited in claim 2 in which said chamber is constituted by an inner wall, a semi-cylindrical housing and a base, said base having a longitudinal channel connecting :a side of said chamber with one of said opposite bores and one of said exhaust bores.

5. A windshield wiper type air motor comprising a semi-cylindrical chamber and a blade mounted for swinging movement back and forth therein, said blade being operable upon actuation of an operating mechanism to swing from an initial stop position adjacent one end of said chamber to a second stop position adjacent the other end of said chamber and then automatically swinging back to its initial stop position and remaining there, comprising a valve housing `formed with an air supply bore, a valve stem-receiving bore, a pair of bores communicating between said air supply bore and said stem-receiving bore, a pair `of bores opposite said rst named pair of bores and a pair of exhaust lbores communicating with said stem-receiving bore, an operating trigger extending over said valve stem-receiving bore, a `valve stem slidably iitted in said valve stem-receiving bore and formed with a pair of longitudinally spaced means permitting the passage of air across said stem, spring means biasing said valve stem into a trigger-opening position closing one of said bores communicating between said air supply 'bore and said valve stem-receiving bore and permitting passage of air through the other of said bores to said chamber on a rst side of said blade and opening the exhaust bore connected with said chamber on the second side or" said blade to atmosphere, latch means for lholding said valve stem against the pressure of said spring means upon depression of said trigger, said valve stem being positioned by depression of said trigger to close the other of said bores communicating between said air supply bore and said valve stem-receiving bore and permit passage of air through the iirst of said bores to said chamber on said second side of said blade and opening the exhaust bore connected with said chamber on the rst side of said blade to atmosphere, and means to release said l-atch to free said valve stem after said blade has swung from one side of said housing to the other side thereof.

6. A windshield wiper type air motor as recited in claim having a rotatable shaft connected to said blade and carrying a sealer pinion, said latch being spring biased against said valve stem and said last mentioned means being movable with said shaft for automatically releasing said latch when said blade completes its initial swing.

7. A windshield wiper type air motor as recited in claim 5 in which said chamber is constituted by an inner wall, a semi-cylindrical housing yand a base, said base having a longitudinal channel connecting a side of said chamber with one of said opposite bores and one of sai-d exhaust bores.

8. A windshield wiper type air motor as recited in claim 5 having a rotatable shaft connected to said bl-ade -and carrying a sealer pinion, said latch being spring biased against said valve stem and said last mentioned means comprises; a cam movable with said shaft for automatically releasing said latch to permit movement of said valve stem to an intermediate position in which said air motor is operative to return said blade to its initial position.

9. In a strapping machine comprising means to supply, position and crimp a seal about the overlapped ends of a strap, the improvement which comprises a jaw support assembly mounted for vertical reciprocation, crimping jaws connected to said jaw support assembly, a sealer pinion rotatably mounted in said jaw support assembly for vertical movement therewith, said jaw support assem- Ibly including means :operated by rotation of said :sealer pinion for :opening and closing said crimping jaws, cam means carried by said sealer pinion and engageable with a cam follower secured to said machine for vertically moving said sealer pinion and said jaw support assembly in response to the rotational position of said sealer pinion and an air-operated motor mounted for vertical movement with said sealer pinion and coupled therewith for rotating said sealer pinion in one direction and then rotating said sealer pinion in an opposite direction back to its initial position, said motor including valve means comprising trigger means, a valve stem Spring biased into trigger-'opening position and latch means mounted to engage said valve stem and Ihold the same upon depression of said trigger.

10. An improvement as recited in claim 9 in which -means are provided for releasing said latch when said ysealer pinion has completed its said rotation in one direction.

11. In la strapping machine comprising means to supply, position `and crimp a seal about the overlapped ends of a strap, the improvement which comprises a jaw support 4assembly mounted for vertical -reciprocation, an `air operated motor yfor controlling the operation of said jaw support assembly, said motor includ-ing ya valve stem movable between a fully closed position in which said motor is held yat rest, a ,fully open position in which air owing to said motor is directed in one direction, and -an intermediate position in which air Flowing to said motor is directed in the opposite direction, Ia lug extending from said valve stem, spring means secured to said valve stem urging said valve stem toward said intermediate and closed positions, a latch having longitudinally spaced notches of different depths, said lug being engageable with said notches to hold said valve stem in :fully open or intermediate position, and a cam rotatable by said motor to position said latch relative to said lug to hold said latch in position to engage said lug as said spring means moves said valve stern from said fully open position to said intermediate position.

12. In a strapping machine comprising means to supply, position `and crimp a seal about the overlapped ends of a strap, the improvement which comprises a jaw support assembly mounted for vertical reciprocation, crimping jaws connected to said jaw support assembly, a sealer pinion rotatably mounted in said jaw support assembly, means operated by rotation of said sealer pinion for opening and closing said crimping jaws, `an lairoperated motor coupled with said sealer pinion lfor rotating it in one direction `and then rotating it in the opposite direction back to its initial position, said motor including a valve housing having a valve stem receiving bore, a valve stem movable longitudinally in said bore, a lug secured to said valve stem, a latch pivoted to said housing land engageable with -said -lug to hold said valve stem in a plurality of diierent ylongitudinal positions in said bore, whereby the air ilow travel through said valve housing 'and said air-operated motor is varied, and a cam rotatable in opposite directions to engage said latch and move it to different operative positions relative to said lug.

References Cited in the tile of this patent UNITED STATES PATENTS 1,764,911 Treat June 17,l 1930 1,777,142 Hueber Sept. 30, 1930 2,210,980 Kathriner Aug. 13, 1940 2,336,264 Leslie Dec. 7, 1943 2,375,769 Childress et al. May 15, 1945 2,497,313 Leslie Feb. 14, 1950 2,661,030 Crosby et al. Dec. 1, 1953 2,802,458 McDonnell et al. Aug. 13, 1957 2,941,782 Winkler June 21, 1960 

1. IN A STRAPPING MACHINE COMPRISING MEANS TO SUPPLY, POSITION AND CRIMP A SEAL ABOUT THE OVERLAPPED ENDS OF A STRAP, THE IMPROVEMENT WHICH COMPRISES A JAW SUPPORT ASSEMBLY MOUNTED FOR VERTICAL RECIPROCATION, CRIMPING JAWS CONNECTED TO SAID JAW SUPPORT ASSEMBLY, A SEALER PINION ROTATABLY MOUNTED IN SAID JAW SUPPORT ASSEMBLY FOR VERTICAL MOVEMENT THEREWITH, SAID JAW SUPPORT ASSEMBLY INCLUDING MEANS OPERATED BY ROTATION OF SAID SEALER PINION FOR OPENING AND CLOSING SAID CRIMPING JAWS, CAM MEANS CARRIED BY SAID SEALER PINION AND ENGAGEABLE WITH A CAM FOLLOWER SECURED TO SAID MACHINE FOR VERTICALLY MOVING SAID SEALER PINION AND SAID JAW SUPPORT ASSEMBLY IN RESPONSE TO THE ROTATIONAL POSITION OF SAID SEALER PINION, AN AIR-OPERATED MOTOR OF A WINDSHIELD WIPER TYPE COUPLED TO SAID SEALER PINION AND MOUNTED FOR VERTICAL MOVEMENT WITH SAID SEALER PINION, SAID MOTOR COMPRISING A BLADE CONNECTED TO SAID SEALER PINION AND MOUNTED FOR BACK AND FORTH MOVEMENT TO ROTATIONALLY OSCILLATE SAID SEALER PINION AND VALVE MEANS FOR REGULATING THE SUPPLY OF AIR TO SAID MOTOR TO CAUSE SAID BLADE TO SWING IN ONE DIRECTION, SAID MOTOR INCLUDING MEANS OPERATIVE UPON SWINGING MOVEMENT OF SAID BLADE THROUGH AN ARC OF ABOUT 180* FROM ITS INITIAL POSITION IN SAID ONE DIRECTION TO REVERSE THE POSITION OF SAID VALVE TO THEREBY CAUSE SAID BLADE TO SWING BACK TO ITS INITIAL POSITION AND TO REMAIN THERE, AND A CONNECTING MEMBER SECURED TO SAID JAW SUPPORT ASSEMBLY AND EXTENDING TO THE SIDE THEREOF REMOTE FROM SAID CAM MEANS AND SAID MOTOR BEING SECURED TO SAID CONNECTING MEANS ON THE SIDE OF SAID JAW SUPPORT ASSEMBLY REMOTE FROM SAID CAM MEANS.
 5. A WINDSHIELD WIPER TYPE AIR MOTOR COMPRISING A SEMI-CYLINDRICAL CHAMBER AND A BLADE MOUNTED FOR SWINGING MOVEMENT BACK AND FORTH THEREIN, SAID BLADE BEING OPERABLE UPON ACTUATION OF AN OPERATING MECHANISM TO SWING FROM AN INITIAL STOP POSITION ADJACENT ONE END OF SAID CHAMBER TO A SECOND STOP POSITION ADJACENT THE OTHER END OF SAID CHAMBER AND THEN AUTOMATICALLY SWINGING BACK TO ITS INITIAL STOP POSITION AND REMAINING THERE, COMPRISING A VALVE HOUSING FORMED WITH AN AIR SUPPLY BORE, A VALVE STEM-RECEIVING BORE, A PAIR OF BORES COMMUNICATING BETWEEN SAID AIR SUPPLY BORE AND SAID STEM-RECEIVING BORE, A PAIR OF BORES OPPOSITE SAID FIRST NAMED PAIR OF BORES AND A PAIR OF EXHAUST BORES COMMUNICATING WITH SAID STEM-RECEIVING BORE, AN OPERATING TRIGGER EXTENDING OVER SAID VALVE STEM-RECEIVING BORE, A VALVE STEM SLIDABLY FITTED IN SAID VALVE STEM-RECEIVING BORE AND FORMED WITH A PAIR OF LONGITUDINALLY SPACED MEANS PERMITTING THE PASSAGE OF AIR ACROSS SAID STEM, SPRING MEANS BIASING SAID VALVE STEM INTO A TRIGGER-OPENING POSITION CLOSING ONE OF SAID BORES COMMUNICATING BETWEEN SAID AIR SUPPLY BORE AND SAID VALVE STEM-RECEIVING BORE AND PERMITTING PASSAGE OF AIR THROUGH THE OTHER OF SAID BORES TO SAID CHAMBER ON A FIRST SIDE OF SAID BLADE AND OPENING THE EXHAUST BORE CONNECTED WITH SAID CHAMBER ON THE SECOND SIDE OF SAID BLADE TO ATMOSPHERE, LATCH MEANS FOR HOLDING SAID VALVE STEM AGAINST THE PRESSURE OF SAID SPRING MEANS UPON DEPRESSION OF SAID TRIGGER, SAID VALVE STEM BEING POSITIONED BY DEPRESSION OF SAID TRIGGER TO CLOSE THE OTHER OF SAID BORES COMMUNICATING BETWEEN SAID AIR SUPPLY BORE AND SAID VALVE STEM-RECEIVING BORE AND PERMIT PASSAGE OF AIR THROUGH THE FIRST OF SAID BORES TO SAID CHAMBER ON SAID SECOND SIDE OF SAID BLADE AND OPENING THE EXHAUST BORE CONNECTED WITH SAID CHAMBER ON THE FIRST SIDE OF SAID BLADE TO ATMOSPHERE, AND MEANS TO RELEASE SAID LATCH TO FREE SAID VALVE STEM AFTER SAID BLADE HAS SWUNG FROM ONE SIDE OF SAID HOUSING TO THE OTHER SIDE THEREOF. 